D-Link DSL-604+ Review

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Introduction

The D-Link DSL-604+ is described as being three boxes in one, an ADSL modem, a 4-port router, and a wireless access point. This is indeed what it is, building and expanding on the original D-Link DSL-504 which we reviewed back in 2001.

The stylish new range from D-Link stands out well with its two colour silver-grey design, and many cooling holes over the top, bottom and sides of the device. The rubber feet provided with the device are movable and can be placed almost anywhere, top or bottom to allow secure stacking of other similarly designed D-Link devices as required, without them moving around should you knock them.

The 604+ has wireless capabilities up to 22Mbps using D-Link’s AirPlus technology, although the PC being used for the review can only support standard 802.11b to 11Mbps. 22Mbps compatible cards can be purchased from DSL-warehouse at a discounted price if buying at the same time as the router. ADSL using G.DMT is supported up to 8Mbps, and there is the ability to use either PPPoA or PPPoE due to be introduced by BT late 2003. It will work with both non-NAT as well as having some more advanced NAT features as described later. Some of the key features also included, are:-

Precise ATM traffic shaping

IP packet routing

VPN pass-through for data protection over Internet

Routing protocol supports RIP-1, RIP-2, Static Routing

Built-in NAT, DHCP server

256-bit WEP/wireless LAN user authentication security

Flow control support for Fast Ethernet

Built-in MIBs for SNMP management

What you get for your money

The package contains the usual goodies as shown above, quick-start user manual, CD-ROM containing full user manual and firmware updating software, RJ-45 patch cable (3m), RJ-11 cable to connect router to micro-filter, and power brick. No micro-filters are included with the router, so these would have to be purchased separately.

At either end of the ports on the rear of the router is an antenna used to improve the reach of the wireless range. They can be twisted 180 degrees from the horizontal and feature a hinge so they can be used sticking directly outwards from the rear of the unit, useful if you decide to wall mount. In attempts to find out if the antennas were removable, it was determined that they contain a wire which reaches up through the plastic shell of the antenna and is hardwired onto the PCB. The other ports from left to right are the 7.5V power input, RJ-14 console port (more on this later), reset button, 4x 10/100Mbps switched RJ-45 ports, and finally the RJ-11 ADSL port.

The front of the router has various indicator LED’s to distract you if you get bored. The standard power LED is first, which is hidden under the word 'Power' printed on the front, and hence sometimes can be hard to see. The presence of the other LED’s should be a good indicator as to whether it is on or not. Next is the status light which seems to flash to indicate that the router is fine, however, the LED doesn’t seem to be in sync with the internal clock/frequency generator in the device and hence seems to flash at a random rate rather than a steady flashing. The ADSL light can be in three states- flashing green, there is activity on the connected ADSL line; solid green, means a connection has been made successfully to the exchange equipment; and off means no connection has been made.

The next set of LED’s refer to the local network traffic. First the WLAN indicator should flash to indicate traffic on the wireless interface, or otherwise be solid green. There are also 2 LED’s which correspond to each Ethernet port. If the left LED only is lit, then a 10Mbps connection has been made; if both the left and right are lit, then a 100Mbps connection on that port. If the left hand LED flashes, it indicates traffic is flowing to or from that port.

Basic Configuration

As with many routers available on the market these days, configuration to get the device working is pretty simple. Once unpacked from the box, connect the necessary wires up that you require. If you have a wireless network card, you can just worry about the RJ-11 cable to the micro-filter and the power adapter. It is not necessary to configure the router first to get a wireless connection working, as this seems to work straight out of the box! Alternatively you can also use one of the 4 10/100Mbps Ethernet ports to create the initial connection if you prefer. Once the router was turned on, and wireless was enabled on the laptop, it took approximately 30seconds to a minute for the laptop to realise that a wireless network was available, with an SSID of 'default'. An IP address of 192.168.0.2 as well as a default gateway and DNS server as set to the default router IP (192.168.0.1) were assigned by DHCP over the wireless interface.

The next step is to configure the router by opening a web browser to its IP address. The first page you are met with is a flash animation depicting a wireless network through a maze. Although this appears quite friendly, the web interface is fairly intrusive, insisting on increasing the dimensions of the Internet explorer window to cover the entire dimensions of the screen (even the taskbar), something I found particularly annoying. The default username and password are both admin, something that is wise to change on your first visit to the webpage.

Unfortunately, the router wants you to reboot after you make any changes to the device, so it is best to do things all at once, and then reboot after you’ve made all the changes.

Once past the initial login stage, the first thing you will see is a page titled "Multiple PVC" (as shown above), with many options beneath it, and a menu bar to the left. This is the main page required to set up the ADSL connection. If you manage to navigate away from it, you can return to it again by selecting "Multiple PVC" from under the "Configuration" section of the menu on the left. If its been shipped with a UK firmware installed, most of the default options will be correct, and the only thing left to change is the username and password. Once these have been entered, click the "Modify" button at the top of the page and it will save this profile under a default name of ISP1, which you can rename as desired.

Assuming you entered the correct username and password, the router should automatically connect you to the Internet and you are then ready and online, free to browse at will. For a simple home network, with just web browsing required, this is all you need do. Testing shows that the web interface is only available on the internal network side of the router, and nothing appears open on the ADSL side by default.

Advanced Configuration

Following through the rest of the configuration menu, we find more options available to us. The first is Ethernet IP address, which has a fairly obvious function. It allows you to change the local side IP address of the router to something that might fit in your network better. If you do make changes to the IP address, to something residing outside the current subnet, it will warn you and ask if you would like to also change the DHCP range that the router is giving out. This is a wise addition to the router as it ensures that any machines gaining IP address by DHCP from the router will be able to migrate easily to the new subnet.

The proxy DNS option allows you to set your workstations to use the router as a DNS server. This is enabled by default, and is in fact what the router uses with its DHCP settings. Although not entirely necessary, if you do an ‘ipconfig /renew’ in a DOS window after the router has connected, the router will also give out via DHCP the DNS servers it has been told about when it created the connection to the ISP.

The next configuration option is for setting up DHCP settings on the local area network. This enables you to customize the IP range that is given out, change DNS servers to a different local or real IP, as well as define a local domain name for use internally. DHCP is enabled by default, and there is an option to disable it as required, if you have your own DHCP server which would be preferred to use.

Network Address Translation (NAT) has several options on the DSL-604+. In default mode, it allows up to 128 clients to use the router as a device to share the Internet connection. This setup is probably the most common used for many small businesses and homes to connect multiple computers to the Internet.

The first NAT menu option allows you to either enable or disable NAT, and also to enable or disable DMZ functions, whilst specifying an IP address. If an IP address is specified and used as a DMZ server, it will basically forward all external ports of the router to this one IP address. This can be useful as NAT has a tendency to break some specific Internet applications such as VPN or video conferencing.

In conjunction with basic NAT and DMZ, it is also worth taking into account the IP masquerade options in the menu. The pass through page has two options, both enabled by default which are related to two different types of VPN- IPsec and PPTP. The options are designed to avoid any NAT functioning on these types of traffic as they pass through the router. How this would hence work, I’m not quite sure, as NAT is designed to rewrite the source IP address from a local IP to the real IP presented externally to the router. If this does not take place, then the server on the Internet would not be able to connect back to the computer behind the router. The masquerade timer page basically defines how long the connection through is remembered by the router once a connection has been made.

The Multi-Nat feature is something not documented in (the current version of) the manual that is available. It allows you to configure the NAT in different ways for different IP addresses on the local network, and works best if you also have multiple static IP addresses from your ISP.

The example above shows how it can be configured for different machines to appear as coming from different IP addresses. The first entry labelled wireless maps the 2 IP addresses 10.0.0.2 and 10.0.0.3 to 123.123.123.2 and 123.123.123.3 respectively, allowing them access to the Internet behind NAT as if configured in the basic mode as described above. The entry labelled wired creates a DMZ mapping for 10.0.0.4 to 123.123.123.4 so any data sent to 123.123.123.4 gets sent to 10.0.0.4. The last entry named banned is being used to demonstrate how to block an IP address from access to the Internet. It does still have access to the other hosts on the internal network however.

Port Forwarding, UPnP and Firewalling

The three aforementioned items are separated onto three separate pages accordingly in the router. ‘Port Redirection’ as it is referred to by D-Link allows the user to set up specific port mappings from the router to another local IP address when using NAT. It is a way of allowing certain traffic inward through the router to the local network without having to adopt routed IP. This is often used to allow the hosting of mail or web servers on the ADSL connection, and can be used if you plan on hosting almost any kind of server.

As with many other routers, the protocols allowed for forwarding are constricted to TCP and UDP. Although this shouldn’t be a problem for most users, it may impose some limitations on what advanced users may be looking to do. Adding port forwarding rules is fairly simple. Ignore the “index to set” field unless you want to modify an existing rule, as the router will increment this automatically. Select the protocol from the pull-down list, and then enter the port number you want to forward in both the start and end port. If you want to forward a range of ports, enter the start and then the end port accordingly and it will allow you to forward as many ports as you like. The local IP address should be set to the IP address of the machine on your network that you want the port forwarded to. The router doesn’t seem to mind if the IP address is outside the subnet of the router, so it is wise to make sure you have typed this in correctly. One option you may have noticed I missed was where it says “Internet” and then has a pull-down list stating “Well-known port.” If we were to stick with D-Link on this, then there are only three well known ports on the Internet! They include FTP (21), Telnet (23) and WWW (80), which does leave this option slightly obsoleted by the start/end port fields.

There is no indication in the user manual as to how many port mappings can actually be entered- I got bored when I reached about 50. Combined with the ability to do port ranges, this should hence cater for all your port forwarding needs. To see the whole list of ports that are being forwarded, there is a slightly clearer table under the “Summary” menu option. This also lists ports that are being forwarded by UPnP.

Although UPnP has its own configuration page, the only options available on it are to enable or disable UPnP. What is UPnP? It stands for ‘Universal Plug and Play’ and allows for the connecting of intelligent networking devices together without user configuration. One main example of this is Microsoft Messenger when running in Windows XP. Messenger is able to communicate directly with the router and open up specific port mappings to allow things like file sending, and video conferencing to work. When this occurs, the port mappings created are listed in gray in the port mappings tables.

Firewalling is handled under the Advanced Filtering and Firewall page, and is disabled by default. Depending how you trusting you are, you can set the firewalling to either allow data to transfer by default unless it is specifically blocked, or you can chose to blocked everything apart from the entries listed. Either the internal (LAN) or external (ADSL) interfaces can be defined in the firewall page to be blocked (or allowed), and the list of protocols includes ICMP, TCP, UDP and ALL.

Ports can only be defined for either TCP or UDP, so if you select ICMP, you will not be able to specify which type of ICMP to filter. You can do a range of ports and also a range of IP addresses (by entering the applicable subnet mask).

Wireless Configuration

One of the main features of the router is the Wireless interface to it which allows you to connect multiple computers with wireless network cards to it. It supports WEP (Wireless Equivalent Privacy) with up to 256bit encryption. All the usual things such as SSID and channel can be set. Channel allows you to set the frequency that the router works on and hence allows you to avoid conflicts with existing wireless networks. SSID is the identifier for the wireless network.

WEP allows encryption of the wireless network which helps stop people from being able to intercept traffic between your wireless device and the router. Additional security is provided in the Access Control section which allows you to either specify the MAC addresses that are allowed to communicate with the device, or those that are not able to communicate.

Wireless reliability seems to be pretty good, however I’ve noticed recently that the router seems to disable wireless every 3hours and then re-enable it. Whether this is a feature or a bug I’ve not yet ascertained, but it is a definite annoyance. It is exaggerated by the ‘intelligence’ of the operating system, in this case Windows XP. Windows XP has a habit of disabling any network interface when it notices that there is no ‘media’ connect to it. As such, if you remove a wired Ethernet cable, it will totally disable that interface and any connections using it will be terminated. The same if the wireless access point cannot be found- all connections are disabled. When using the laptop booted into SuSE, the connection drop was less than a second so was not noticed, but Windows has enhanced this to be more like 20seconds by the time it reconnects. This could be a firmware issue, and the version that is currently being used is b3t18uk.

I attempted a firmware upgrade to the latest version to see if this could fix it. A note for all readers- If you attempt a firmware upgrade, ensure that network cables are firmly plugged into the router and ensure that they will not come out. If this happens during a firmware upgrade you’ll end up with a dead router such as mine which was not recoverable. Although D-Link do provide you with a console port, this isn’t much use as it requires an RJ-14 – serial cable. I’ve been hard pushed to actually find an RJ-14 cable, and if you eventually do, you’ll also need a BOOTP/TFTP server, and a copy of the firmware in binary form (I’m as yet unsure if this is the same as the version available from the D-Link ftp server). D-Link will swap out the unit for you if it is within 30days of purchase. After that it is to the discretion of your hardware provider as to what to do.

DSL-warehouse were very prompt at sending out a replacement unit, it arriving two the day after they received the faulty unit. Following receipt of the replacement model, and again (this time successfully) updating the firmware, to the latest (b3t25uk). This did prove to fix the 3hour disconnections on the wireless side, so anyone with this problem a firmware update should sort it out.

Our standard wireless distance test was completed and attained a reasonable score of 16 out of 20, comparing well with similar competing products such as the Netgear DG824M.

Hardware Used

Score out of 20

ELSA Lancom wireless access point, PCMCIA card

10

Asus 6030VI modem/router

13

Linksys WAP11 access point

15

Linksys WET11 access point

16

Solwise SAR-715PVW, PCMCIA card antenna

12

Netgear DG824M

16

BT Home Network 1200

17

BT Voyager 2000

13

Vigor 2600We

18

D-Link 604+

16

A second more extensive test was completed showing a true comparison of speeds with the wireless devices placed in the same position for each test. This should over time provide a better indication of performance rather than a simple score.

Hardware Used

1m

5m + 2walls

8m+4walls

8m+4walls and floor

75m outside

100m outside

150m outside

D-Link 604+

11

11

11

1-2

6

11

1

Buffalo Airstation with 54G

54

54

36

11

36

48

1-5.5

Buffalo Airstation in 802.11b mode

11

11

4

1

2-11

11

1

The common drop at 75m outside for all devices is likely due to the angle at that location since its not possible to keep the laptop at a level height throughout all distances.

General

The router survived well under a refresh of Counter-Strike servers in game which is something that has previously plagued some routers with the NAT translations table being flooded with too many entries. Ping responses using the [email protected]_domain username to first hop were disappointing, with a first hop of 22ms, the highest of all that we have tested to date, as shown by the comparison table here:

The router has a few other small features such as a date/time page to sync the router with an NTP source, or with the current PC’s time. I found when trying to set it to a local NTP server it continually failed, and ended up thinking it was still back in the 1970’s. Perhaps this was a problem with the ‘save all and restart’ option on this page. If you ignored this and chose to manually save the settings and restart the router I found it stored the server correctly. There was also a problem with it chronically changing the IP I put in for the local NTP server to something similar, but not in my subnet which seemed strange to say the least.

The user manual distributed on the CD is pretty comprehensive detailing how to do specific setups with the router and explaining each individual page in the router. It is somewhat out of date, so some new features added by updated firmware may be missing. The manual also seems to be based on that for the DSL-504 as there are several references to the DSL-504 router which have made their way in.

Diagnostics features included in the router do include a line conditions page which details your attenuation and signal to noise ratio dB readings which can be useful to know if a fault appears on your line. For example, if you note the attenuation figure you normally have, you may notice a rise of perhaps 10dB which might indicate a potential problem on the line between your router and the exchange equipment.

There is also a carrier chart which shows the signal quality of both the upstream and downstream frequencies being used by the router. A word of warning though, don’t play with this page too much as I got it to crash the router once or twice whilst loading the java applet. The corresponding graph to the data above is as here:

To compare with another 2Mbps ADSL line, the following graph is a sample of what else could be seen.

Verdict

All in all, the router performed well with a few issues here or there that could do with improvement. The Multiple PVC page should let you keep your settings from previous encapsulation types as it blanks out all the fields if you change this option. The user interface is not the easiest or most esoteric to use, and it is probably aimed at the more technical user base than some of the similar featured rivals such as the Netgear DG824M or the BT Voyager 2000 Wireless.

The DSL-604+ provides a good feature range combined with 22Mbps wireless networking at an intermediate price range, ideal if you don’t need as much as 54Mbps wireless and want to stick with just a single integrated box.